It was the worst man-made environmental disaster in the nation's history, but unlike other calamities of nature, this one took only 40 or 50 years to create. And once it started, it lasted a decade, claimed many lives, either through "dust pneumonia" or suicide, and taught us very little about taking the long view of our land over the opportunity for quick financial gain.

Ken Burns' "The Dust Bowl," a four-hour documentary airing in two parts Sunday and Monday, is not one of his better films by any means, but it makes its basic points and, more important, gives us an oral history from members of the generation who lived through the "dirty '30s."

Written by longtime Burns collaborator Dayton R. Duncan and narrated by Peter Coyote, "The Dust Bowl" is, alas, well timed: It was only this summer that the Midwest was hit with an extended drought, serious enough to evoke memories of the rainless 1930s.

While the Dust Bowl affected much of the Midwest from 1931 to the end of the decade, ground zero for the devastation was Boise City, a small city in the Oklahoma Panhandle known as "no man's land." Over the decade, the overall area of greatest devastation shifted like an amoeba on the map, but the hardest-hit areas remained the Oklahoma and Texas panhandles, the southwestern corner of Kansas, northeastern corner of New Mexico and the southeastern corner of Colorado.

There's no small irony in the fact that for several years before the drought hit, farmers in these areas were enjoying boom times. Their wheat crops were abundant, and there was a good market as well. But almost as a feast-before-famine harbinger, the bottom fell out of the wheat market when the Great Depression hit, forcing farmers to dump their grain on the streets.

In 1931, it stopped raining.

While the decade of drought was obviously a natural phenomenon, the Dust Bowl was caused by farming and, in specific, by innovations that enabled farmers to plow up a lot of land in a short period of time. Once the grasses of the Great Plains were replaced by crops, the stage was set for the devastation that would come when it stopped raining. Crops dried up or didn't grow at all, and winds sweeping down from the north and west were able to carry the topsoil away in huge "black blizzards," until what was left was earth likened to a floor of concrete by the Dust Bowl survivors interviewed in the film.

Farmers' perseverance

Farmers, we're told, are always "next-year people." If a crop isn't bountiful this year, or there's not enough rain, well, there's always next year. This is what makes them survivors. You have to be in order to be a farmer because there are things you just can't control. So many people stayed in the Dust Bowl states and didn't follow the escape route to California because there was always next year. Their hope diminished year after year, of course, but they stayed because that's what farmers do.

Vintage photographs and film add enormously to our understanding of the Dust Bowl, using the term coined by journalist Robert Geiger after the infamous Black Sunday dust storm of April 14, 1935. And the interviews with people who were mere children when the drought and dust hit are convincing and eloquent in their simplicity, as opposed to the windy script by Duncan and Coyote's usual funereal intonation.

We hear an elderly man speak about the death of his precious young sister, the only girl in a family of boys. She died from "dust pneumonia" the same time the disease claimed the family matriarch. The family had to transport the toddler's body to Enid, Okla., for burial because no one could even see the tombstones anymore in the Boise City burial ground to find an unused spot for a child's grave.

A woman recalls her father having to club a young calf to death because there was too little milk to support both the animal and his little girl. These stories stick with you because they are told by people who were there. It's no small irony that at the end of the film, the names of several participants are included in an in memoriam list. The generation of Dust Bowl survivors is gradually dying off.

In the long run, the end of the Dust Bowl came only when it started to rain again, but in the meantime, the federal government did what it could to help, first by teaching farmers how to minimize their land's vulnerability to the winds by employing contour plowing, and then through relief efforts like the Civilian Conservation Corps, the Works Progress Administration and the Resettlement Administration.

As we'd expect from our vantage point, the New Deal efforts were controversial. Many opposed them, calling CCC projects "make-work" and "boondoggle." But as the Dust Bowl survivors saw it, those who were able to find jobs and feed their families through the projects supported the New Deal and Franklin Delano Roosevelt, who gave a major outdoor speech at the end of the '30s in Amarillo, Texas, attended by thousands.

As he spoke, it started to rain.

Like Burns' 2011 "Prohibition" documentary, "The Dust Bowl" has implicit cautionary advice for our own times. In this case, the advice is don't ravage the environment in your quest for profit because the damage can't be repaired. Today, farmers in the Great Plains have some protection against drought because of the Ogallala Aquifer, a shallow underwater "pond" that stretches from South Dakota to north Texas and is used for irrigation.

But half the water in the aquifer is already gone, and the rest could disappear in 20 years. Even with the water from Ogallala, we saw only last summer the damage drought can do to crops and livestock.

Too much repetition

But as a film, "Dust Bowl" is sadly lacking. It's in dire need of tighter editing, most of all. Yes, the images from the '30s are powerful, but after a while, their power is diminished by repetition. The script is informative, but it's also so full of itself, you're even more grateful when you get to listen to the people who were actually there, as opposed to the solemn tones of Coyote reading Duncan's bloviated, redundant prose. There's also a section of the film about how the Okies were treated in California. It's interesting for a few minutes, but very soon begins to feel beside the point and, again, in need of editing.

But this is how Ken Burns makes films. He has a template and rarely varies from it. When he gets carried away and isn't sufficiently detached to make needed cuts and to sharpen his focus, we get "The Dust Bowl" or "The National Parks: America's Best Idea," a six-part slog that made you want to fell every tree in Yellowstone.

"Dust Bowl" isn't quite that bad, not just because it's not as long, but because of the people who were there. Their simple words and detailed memories make this film necessary. Even all these years later, you can see and hear how fresh the memories remain, and it breaks your heart.